Cis-difunctionalized 21-telluraporphyrin building blocks and their use in the synthesis of (BODIPY)2-telluraporphyrin triad

Abstract

A series of cis-difunctionalized 21-telluraporphyrins containing two functionalized meso-aryl groups such as [Formula: see text]-iodophenyl, [Formula: see text]-bromophenyl, [Formula: see text]-cyanophenyl, [Formula: see text]-nitrophenyl and [Formula: see text]-trimethylsilyl ethynylphenyl groups in cis-fashion were synthesized by condensing one equivalent of 16-telluratripyrrin with two equivalents of functionalized benzaldehyde and three equivalents of pyrrole in CH2Cl2 under acid catalyzed porphyrin forming conditions. The cis-difunctionalized 21-telluraporphyrins were thoroughly characterized by HR-MS, 1D and 2D NMR, and absorption spectroscopic techniques. To show the use of cis-difunctionalized 21-telluraporphyrin building blocks, the covalently linked (BODIPY)2-telluraporphyrin triad was synthesized by coupling cis-diiodophenyl 21-telluraporphyrin with meso-ethynylphenyl BODIPY under Pd(0) coupling conditions and afforded (BODIPY)2-telluraporphyrin triad in 24% yield. The NMR and absorption studies of the triad indicated that the telluraporphyrin and BODIPY moieties interact weakly in the (BODIPY)2-telluraporphyrin triad and retain their individual characteristic features. The steady-state fluorescence and DFT studies indicated a possibility of charge transfer between 21-telluraporphyrin and BODIPY units in the triad.